A printed circuit board serves as a support chassis for various discrete electronic components, such as integrated circuits, resistors, capacitors, and other components. The printed circuit board also provides the copper or other metallic conductors for conveying electrical current between the connected terminals of the electronic components. Conductors on opposite sides of the flat substrate or insulator of the board are frequently connected by plated through-holes. Plated through-holes are also useful when soldering components to the printed circuit board. Plated through-holes are created by plating copper or some other metal onto the side walls of the holes formed through the circuit board insulator or substrate, between the conductors on opposite sides of the substrate.
In the prior art, plated through-holes are produced by a complicated and time consuming process utilizing a series of chemical dipping vats and processes. Many different vats are usually used, and the chemical composition and conditions of many of these vats must be separately maintained within relatively critical tolerances. The criticality of the various prior art processes involved, and the various disadvantages associated with the prior art processes are briefly described in the aforementioned patent application Ser. No. 929,390.
The prior application Ser. No. 725,817 describes a technique used in producing printed circuit boards by employing a computer controlled plotter. Using the technique described allows printed circuit boards to be produced conveniently and quickly. The prior application Ser. No. 929,390 relates to one method of forming plated through-holes which can be employed to make printed circuit boards with the computer controlled plotter. The resent invention relates to another technique of forming plated through-holes which can be employed in conjunction with the computer controlled plotter technique as well as with other independent, larger scale techniques of making printed circuit boards with plated through-holes.